Airlines pulled in extra, larger aircraft to help thousands of people leave Tokyo and European carriers began screening aircraft and crew for radiation as Japan rushed to prevent a nuclear disaster.

Airlines pulled in extra, larger aircraft to help thousands of people leave Tokyo and European carriers began screening aircraft and crew for radiation as Japan rushed to prevent a nuclear disaster.

As an increasing number of governments from Britain to New Zealand to South Korea advised citizens to leave quake-affected northern Japan, airlines mobilised for mainly outbound traffic from one of the world’s biggest cities.

Japan has been taking measures to contain a crisis at the Fukushima nuclear power plant crippled by the earthquake and tsunami that devastated the northeast on Friday. The US State Department said the government had chartered aircraft to help Americans leave Japan and had authorised the voluntary departure of family members of diplomatic staff in Tokyo, Nagoya and Yokohama.

"The situation has deteriorated in the days since the tsunami and ... the situation has grown at times worse with potential greater damage and fallout from the reactor," White House spokesperson Jay Carney said.

The US travel advisory came after Australia urged citizens with non-essential roles in Japan to consider leaving Tokyo and the eight prefectures most damaged by the earthquake due to infrastructure problems rather than nuclear concerns.

Air India increased flights and used bigger planes to help bring back Indians from Japan. It has been using a Boeing 747-400 jumbo jet with a capacity of 423 passengers, instead of a smaller Boeing 777-300ER.

Britain said it was chartering flights from Tokyo to Hong Kong. Britons directly affected by the tsunami will be offered the flight for free. France and Germany have also advised citizens in Japan to get out or head to southern Japan.

Health authorities in several countries responded to concerns about the possible health impact from radiation starting checks on people, planes and boats. There were no immediate reports of contamination, although officials in South Korea and Taiwan said some passengers arriving from Japan had been observed with slightly higher levels of radiation.

Commercial flights were under pressure, with just handful of seats left on most services from Narita — which serves Tokyo — to Hong Kong, Singapore or Seoul. Demand was driving the average price of a one-way ticket above $3,000, far higher than normal price.